The present invention relates to a semiconductor integrated circuit and a position detector.
Regarding a position detector such as a digital vernier caliper, a digital micrometer, a digital indicator and the like, a position detector using a general battery cell as a power supply and a position detector using a solar cell as a power supply have been known.
As compared to an output voltage of the general battery cell, an output voltage of the solar cell is unstable. Therefore, when configuring a position detector using a solar cell as a power supply, it is necessary to mount an electrically rewritable non-volatile memory such as an electrically erasable programmable read-only memory (EEPROM) so as to preserve information such as an origin and a unit.
Also, the position detector using a solar cell as a power supply requires a power supply control circuit corresponding to the solar cell. The power supply control circuit is configured to stabilize the output voltage of the solar cell by using a voltage regulator, thereby outputting a reset signal when a power supply voltage is lowered.
Patent Document 1 discloses an absolute displacement measuring device using a solar cell. The absolute displacement measuring device disclosed in Patent Document 1 has a solar cell, and a power supply voltage control circuit configured to stabilize a power supply voltage supplied from the solar cell and to supply the same to each unit.
[Patent Document 1] Japanese Utility Model Registration No. 2,571,356
In order to reduce a manufacturing cost in a manufacturing process of the position detector, a position detection IC having a power supply control circuit, which corresponds to a solar cell and a general battery cell, has been developed. The developed position detection IC has the power supply control circuit. However, when the position detection IC is mounted on a position detector configured to operate by a general battery cell, a function of the power supply control circuit is stopped. That is, since the position detection IC of the position detector configured to operate by the general battery cell is added with the cost of the unnecessary power supply control circuit, the price thereof is increased.
In order to further reduce the manufacturing cost of the position detector configured to operate by the general battery cell, it is preferable to manufacture a position detector having a position detection IC not including a power supply control circuit.
However, according to the position detection IC mounted on the position detector, it is necessary to reset a digital circuit of the position detection IC upon activation of the position detector so as to prevent a malfunction. In the position detector using the general battery cell as a power supply, it is expected that a power supply voltage rises rapidly upon connection of the cell. Therefore, it is possible to reset the digital circuit of the position detection IC (Integrated Circuit) by mounting a simple power-on-reset circuit using a CR (Resistor Capacitor/Condenser) time constant. Meanwhile, in the position detector using the solar cell as a power supply, it is not possible to use the power-on-reset circuit using a CR time constant because the power supply rises gently.
Due to the above reasons, it is difficult to manufacture a position detector using both a general battery cell and a solar cell as a power supply and having a good quality at a low price while reducing the manufacturing cost.